1. Field of the Invention
This invention relates to an electrochemical treatment for selective metal deposition or removal.
2. Description of the Prior Art
In electrochemical plating processes, particularly those processes carried out in a continuous manner, it is desirable to deposit metal on an article as rapidly as possible. In addition, some metals are more difficult to plate rapidly than others. In particular, the deposition of gold to a usable depth is typically a more time-consuming process than plating of such metals as nickel, or other processing steps such as polishing. This implies that gold electroplating is typically the limiting factor in the processing speed of continuous strip-plating apparatus such as that described in U.S. Pat. No. 4,153,523 assigned to the same assignee as the present invention.
Furthermore, with the high cost of such metals as gold, it is necessary to limit the deposition of these metals to selected portions of many articles, such as electrical contact terminals. Various other uses are made of selective metal deposition, such as the production of circuit boards, relay contacts, etc. It is therefore desirable to have an electrochemical processing cell that can rapidly plate metals onto well-defined portions of articles.
To obtain high speed gold plating in well-defined regions, the prior art typically uses a spray nozzle which also serves as the anode and directs a spray towards a masking plate; see, for example, U.S. Pat. No. 4,029,555. It would be advantageous to further increase the plating rate of gold-plating cells that selectively define the portions of the object to be plated, while obtaining increased design freedom both for the plating cell and the article to be plated.